Police arrested one suspect Monday and are asking for the public's help in identifying a second suspect who pepper sprayed and tried to rob a hearing-impaired foreign exchange student on a San Francisco Municipal Railway bus last month.

The attempted robbery occurred at about 5:35 p.m. on Oct. 20 on an inbound 38-Geary bus near Market and New Montgomery streets, police said.

Suspect Raheem Muhammad, 24, of Oakland, and another suspect were on the bus and allegedly approached the 24-year-old victim, pepper sprayed him and tried to steal his backpack, according to police.

The victim was able to hold onto the bag and the two suspects fled. Officers quickly arrested Muhammad, but the second suspect, who has not been identified by investigators, fled and remains outstanding.

Bus security footage captured an image of the second suspect just prior to the robbery. He is described as a black man in his 20s who is about 6 feet 1 inch tall, weighs 150 pounds and was wearing a brown sport coat and brown pants.

Anyone who has information about the suspect's identity or whereabouts is encouraged to call the Police Department's Muni task force at (415) 832-8338.

People wishing to remain anonymous can call the department's tip line at (415) 575-4444 or send a tip by text message to TIP411.

Muhammad remains in custody on attempted robbery and conspiracy charges, police said.