HAYWARD, Calif. -- While the relatives of a Hayward man slain in an officer-involved shooting at a BART station gathered to bid him farewell Wednesday, emotions flared in the surrounding community.

Hundreds of family members and friends filled Hayward’s Palma Ceia Baptist Church to bid a tearful farewell to Oscar Grant III. But it wasn’t only emotions that filled their hearts and minds. It was the question of why this happened to the grocery store employee and father.

“It’s unbelievable,” Yolanda Mesa, the sister of Grant’s girlfriend, told KTVU.

“I’m sad, torn apart. (I’m) keeping my sister and niece and his mother in my prayers, hoping they will hold up…They are taking it really hard… There’s hurt and for me there is definitely anger. I’d be lying if I said there wasn’t.”

“He didn’t deserve this. He was a father, he worked, he just adored my sister… They could not live without each other. He was a good man, he did everything he was supposed to…He gave my niece the best Christmas this past year.”

The Rev. James Word said, "I thought Oscar was going to be a preacher but God had other plans."

Word recalled that Grant, who worked as a butcher at an Oakland grocery store, came to his office one day to tell him how happy he was when he became an apprentice meat cutter.

The Rev. Ronald Coleman, who presided at the funeral service, said, "this is something that the world is watching. They wonder if we will start a fight or a civil commotion."

But Coleman told the audience, "We must respond with prudence."

Coleman said, "I understand that some of you youngsters are upset, but nonetheless we have to trust in God. This is not your fight."

While Grant was remembered by his family and friends, community leaders were voicing outrage over the shooting and ensuing investigation. The leaders gathered outside the Alameda County courthouse in downtown Oakland and then crowded into the District Attorney’s office demanding some legal action.

“Justice delayed is justice denied,” Oakland City Councilwoman Desley Brooks told the crowd at the courthouse. Grant III was killed by a BART officer in a controversial shooting as he was being detained on the ground by fellow officers.

Bay Area Rapid Transit trains were passing through the Fruitvale station without stopping Wednesday afternoon because of a protest taking place there, a BART dispatcher said.

Groups rallied at the station to protest Grant's shooting death after his funeral.

For safety reasons, the trains will pass through the station in both directions without stopping until the crowd leaves, a dispatcher said.

The fatal shooting was captured on cell phone videos by several bystanders at the station and on a train stopped on a nearby platform. Closeups of several frames of the video show Grant's hands behind his back. BART officials have not neither confirmed nor denied that Grant was handcuffed at the time of the shooting.

Oakland Mayor Ron Dellums issued a statement Wednesday offering condolences to Grant’s family but also asking for calm.

“Our entire community grieves at the loss of Oscar Grant III,” Dellums said in the statement. “I am profoundly saddened by the turn of events that resulted in the loss of a young man’s life which has left a family and a community in mourning.”

“Our hearts and deepest wishes for peace go out to the families and loved ones of all the parties involved in this tragic event. While the investigation now underway may shed light on specific details of the shooting, at the end of the day, establishing culpability will not bring back a life tragically lost.”

Hours earlier, the officer who fired the fatal shot -- Johannes Mehserle -- failed to show up for a scheduled meeting with BART investigators and instead resigned from the transit agency's police force.

In a news release, BART spokesman Linton Johnson said the officer – identified in a civil complaint as Mehserle – had through his attorney attempted to defer the meeting with investigators until next week.

BART investigators declined the delay. At Wednesday's meeting, Mehserle’s attorney and his union representative submitted his resignation letter. He was not present.

BART officials have notified the Alameda County District Attorney’s Office of the resignation.

BART had told KTVU on Tuesday that Mehserle had received death threats and was currently under police protection. The threats have forced him to be moved twice.

Earlier Tuesday, Grant’s family alleged in a $25 million claim that the BART officers violated had violated the slain man’s civil rights, illegally detained him and used excessive force.

The claim, filed by attorney John Burris on behalf of Wanda Johnson, Grant's mother, and Sophina Mesa, the mother of Grant's 4-year-old daughter, also named the BART police officer who shot Grant as Mehserle.

Grant, who worked as a butcher at an Oakland grocery store, "was unarmed and offered no physical resistance to BART police officers" before being shot shortly after 2 a.m. on Jan. 1, according to the claim.

Mehserle is seen on at least two video tapes firing his gun into the back of Oscar Grant as Grant lay on the floor of the Fruitvale BART station.

Burris says there are four videos of the shooting he knows of which bolster his case against BART and the officer.

"There's no such thing as a slam dunk other than basketball, but in terms of the case itself, we have very compelling evidence," said Burris

Still frames from video of the scene show Officer Mehserle minutes before the shooting. He appears to be wearing a Taser on his left hip and a gun on his right. There is also a female officer nearby with a Taser out of its holster and in her hand.

At one point, it appears Mehserle has drawn his Taser and is standing over Grant. Witnesses claim they heard Grant pleading with police to not be tasered.

Attorney Burris says the pictures not only show the shooting was unjustified, but that Mehserle should be charged with a crime.

"The videotape that we see where the person is being shot in the back while he is on the ground and not commiting a danger to the officer," said Burris "That's criminal conduct. To me that's murder. That's second-degree murder. "

Mehserle now has an attorney, but his attorney did not return phone calls to KTVU for this story.

A closer look at images taken from video shot during and after the incident raise troubling questions about the actions of Mehserle in the moments before his gun fired.

Engineer Devinder Grewal specializes in failure analysis and accident reconstruction. Tuesday, he examined videos obtained by KTVU that seem to indicate Mehserle drew a Taser at least once before the fatal shooting. Mehserle’s actions raise questions about whether the officer was confused about which weapon he was holding when the gun fired.

"I would want to look at this and try to make a diagram of where the people are and how they're moving," said Grewal. "If the facts as we know them now are true, then this means that he did manage to take the Taser out from the left-hand side with his right hand and had it on his right-hand side before the shooting. Then -- at some point -- the Taser is gone. It's either back in its holster or it's gone because he's got his gun in his right hand."

Mehserle graduated from the Napa Valley College Criminal Justice Training Center in 2006.

Center Director Damien Sandoval says instructors here emphasize defensive tactics such as when to use a weapon and what type to draw.

"Both at the academy training level and in the departments, we do a lot to make sure the officers are aware of weapon placement on their utility belts," explained Sandoval.

Still, Sandoval says there is always a potential for confusion in melees such as the one on the BART platform New Year's Day.

"It's really disconcerting when you see a group of people -- both officers and civilians -- acting in the confusion that's surrounding them," said Sandoval. "So I really was struck by the amount of stress that was put upon everyone that was involved in that situation."

Mehserle has not yet spoken to BART investigators. Legal experts say Mehserle has a Fifth Amendment right not to do so. BART investigators are likely talking to others involved in the shooting.

"They're probably talking to the other officers who were there that night, trying to find out if there was anything unusual about that officer," said San Francisco criminal defense lawyer Steven Gruel. "Was he acting strange, or saying anything that would be unusual? They're probably talking to that gentleman who was sitting down at the scene apparently cuffed near the incident."

Gruel said the availability of these videos could actually hinder investigators interviewing those caught on tape that morning.

"It allows those who were there to know that video is out there," explained Gruel."They see themselves and they may try to maybe fashion a story to meet what's seen visually."

Gruel told KTVU the $25 million dollar lawsuit Grant's family has filed against BART is "an extremely strong case."

BART has told KTVU it is investigating the incident and has asked that people not jump to conclusions. BART has 45 days to respond to the legal claim filed Tuesday. If BART rejects it, as Burris expects, he says he'll file a civil rights lawsuit in federal court.

BART has told KTVU it is investigating the incident and has asked that people not jump to conclusions.

Tuesday night, a BART spokesman said attempts have been made to interview Mehserle, but that his attorney has "stonewalled" and not made him available.