Friends and family are mourning the death of a 37-year-old transgender woman who was shot to death Sunday while she was parked in a car in downtown Oakland with three transgender women friends.

Tiffany Woods, the victim's former supervisor at the Tri-City Health Center in Fremont, said her large group of friends is devastated by the death of Brandy Martell, who had long been living as a woman.

Police said the victim was born as Milton Massey Jr., of Hayward. The victim was shot and killed about 5:20 a.m. Sunday while sitting in a car at 13th and Franklin streets. Authorities wouldn't disclose further details.

No one else was injured.

Woods said the victim had a large circle of friends, many of them younger transgender women who admired Martell.

"In the world of transgender women of color, she was successful," Woods said. "She had a job, she had a car, they looked up to her, (and) she was beautiful. They are shocked."

A public funeral is planned for 11 a.m. Wednesday. at C.P. Bannon Mortuary at 6800 International Blvd. in Oakland. A celebration of Martell's life will be held later this month.

Woods supervised Martell for four years while she worked as a peer advocate for TransVision, which provides services for transgender people. Martell worked for the program from February 2007 until November, when program funding was cut and Martell was laid off, Woods said. Martell also helped organize five annual Alameda County Transgender Day of Remembrance events in Oakland over the past several years.

Woods said the group of friends had been sitting in the car socializing because they are not welcome at bars and clubs that cater to gay or straight people and wanted to spend time together on Saturday night, which stretched into Sunday morning.

Woods said transgender women are involved in "active sex work" downtown, especially on Martin Luther King Jr. Way between 12th and 17th streets, but that the victim was not involved in prostitution.

Woods said the witnesses in the car -- who police have not identified -- said two unknown men came up to the car and started a flirty conversation with the group several hours before the killing. Woods said the men did not realize the group was transsexuals, and when they were told, they left. But later they returned. There was a verbal confrontation, and one man fired into the car, killing Martell, who was in the driver's seat. Woods believes the shooting was a hate crime.

"Brandy was loved and valued by all of her co-workers at Tri-City Health Center, and all are shocked and saddened by the news of her death," Woods said in a statement. "Our collective hearts and prayers go out to her family, friends and community members."

Police have not released a motive in the killing.

Authorities said a hate crime is one possible motive they are investigating because the gunmen were upset after learning Martell was not female. No arrests have been made. Reached at their home in Hayward, the victim's parents declined to comment.

The last reported murder of a transgender person in Oakland was in November 2003, when 38-year-old Stanley Traylor, a biological man, was shot to death in West Oakland. He was found dressed in woman's clothing and wearing earrings.

A wig was found nearby. The case has never been solved.

Hate crimes against people in the lesbian, gay, bisexual and transgender community are on the rise.

The 2010 Hate Violence Report from the National Coalition of Anti-Violence Projects shows murders of LGBT people rose 23 percent from 2009 -- when there were 22 such murders -- to 2010, when there were 27. Of the victims, 70 percent were people of color, and 44 percent were transgender women.

The report is the latest data available.

Staff writer Harry Harris contributed to this report.