TIBURON, Calif. -- Neighbors of 75-year-old Joan Rosenthal, who was found shot to death outside the front door of her Hilary Drive home in Tiburon Tuesday morning, remembered her Wednesday as a good neighbor and an active member of the community.

Police are investigating her death as a homicide but have not yet released more information on the case. An autopsy was scheduled for noon Wednesday.

"She was a very good neighbor," Kathy Keating said. "Our children grew up together. She was a very meticulous person and was well-organized."

Keating said she and other neighbors initially thought Rosenthal lost her balance and fell before police disclosed she had been shot in the head.

"We are all up in age and tend to lose our balance more," Keating said.

Keating said none of the neighbors heard a gunshot.

"I can't image anyone who would hurt her," Keating said.

Rosenthal's husband, who suffered from Alzheimer's disease died in January, Keating said.

"She still had so much to live for," Keating said.

Sally Shepard said she was friends with Rosenthal for 44 years.

"She was extremely active in many ways. She got her master's degree in career counseling and taught classes at the College of Marin. She was a trained speech pathologist," Shephard said.

"We walk almost every day. She has five grandchildren who are the love of her life, two sons and two daughters-in-law. They were an extraordinarily close family," Shepard said.

"She was a quiet contributor. You did not see her picture in the paper," Shepard said.

"I was with her the night before. She had health problems in the past year that somewhat limited what she could do," Shepard said.