A series of fires, including three last weekend, prompted an investigation by San Francisco's arson task force.

This isn't Diaz's first encounter with San Francisco law enforcement.

Last August, a Superior Court jury convicted him of involuntary manslaughter in the June 2011 death of a sexual partner in Buena Vista Park. Prosecutors said Diaz set the victim's body on fire after strangling him and had sought a conviction on a charge of first-degree murder.

Diaz's attorney argued the victim, 23-year-old Freddy Roberto Canul-Arguello, asked to be choked during a sexual encounter. Diaz reluctantly agreed, said Deputy Public Defender Alex Lilien, and accidentally asphyxiated him. Canul-Arguello's body was burned, the defense said, when Diaz lit the contents of a recycling bin to signal for help. Diaz also reportedly called 911 and pulled a nearby fire alarm box before leaving the scene.

Diaz, who had been jailed since his arrest in 2011, was released from custody last September. Two months later, a judge sentenced Diaz to four years and eight months in state prison -- but he remained free because of time served and good-conduct credits.

San Francisco Public Defender's spokeswoman Tamara Aparton said Thursday the office expects to represent Diaz in the new case.

Supervisor Scott Wiener, who represents the area where the recent arson fires took place, said he was happy to hear that someone was in custody.

"The arsons that have been happening in the Castro in the last few months have been very scary," Wiener said. "I hope that they got the right person," Wiener said. "I hope that these arsons stop."