A homeless man was charged Wednesday with a string of stabbings against women and children as they rode Muni or walked the streets of San Francisco.

Bobby L. Brown Jr., 30, faces four counts of attempted murder, four counts of assault with a deadly weapon and seven other felony charges stemming from the unprovoked attacks, including one Monday.

District Attorney Kamala Harris said all four attacks - and two more that are being investigated as potentially involving Brown - appear to be random, targeted at vulnerable people and committed with no motive.

"We are ending tonight this defendant's reign of terror," Harris said Wednesday night. "We've got our guy, and he's off the streets."

Harris said Brown faces 72 years to life in prison if he is convicted.

Rachel "Ty" Brown, 24, who is not related to the suspect, was stabbed on the J-Church streetcar as she slept on the way to school. Prosecutors say Bobby Brownattacked her with a corkscrew found in his pocket when he was arrested Tuesday. Authorities believe he used a knife in the three earlier incidents.

The first occurred on Sept. 1, when 11-year-old Hatim Mansori was repeatedly stabbed as he rode home from baseball practice.

Bobby Brown's mug shot had been in a group of photos the boy was asked to review after leaving the hospital, but he was unable to identify him. Unable to make a case against Bobby Brown, San Francisco police turned him over to San Mateo County authorities on an outstanding warrant in an indecent exposure case.

The boy's mother, Laila Elfazouzi, said Wednesday that her son had been asked to assist police in making an identification this week.

She said she was frustrated in how long it took to capture a suspect. "It takes so long, meanwhile, he hit another victim, the lady, it's very sad," she said.

The attacks escalated after Bobby Brown was released from jail in San Mateo County on Nov. 10, authorities said.

He pleaded guilty to two misdemeanor charges and was put on probation. He was later charged with misdemeanor battery of a San Mateo sheriff's deputy while in custody.

Four days after his release, prosecutors say, on Nov. 14, Bobby Brown allegedly stabbed a 25-year-old San Francisco woman at Sutter and Jones streets at 10:40 a.m. after she refused to give him money. She was stabbed twice in the back and buttocks and was hospitalized.

On Thanksgiving Day, Nov. 26, he allegedly attacked a 26-year-old woman in the Tenderloin at Golden Gate and Leavenworth streets in front of her three young children, one of whom she was pushing in a stroller.

Prosecutors said Bobby Brown grabbed the victim for no apparent reason and stabbed her three times in the back. She was hospitalized for seven hours.

"I feel like there's been some closure," said the victim, who asked not to be named. "I feel utterly grateful that I am alive today. That guy could have taken my life.

"He's sick - anyone in this world who would just randomly attack a woman with three small children is sick. "

Police Commander John Loftus said police were able to link the attacks because they were all stabbings, all random, the locations were all clustered in the city's central neighborhoods and the victims' and witnesses' descriptions of the attacker all matched up.

Loftus said two other stabbings are being investigated in connection with Bobby Brown, and that anybody who knows of similar attacks should call the police department's tip line at (415) 575-4444.

Harris said she could not discuss the defendant's mental state, but that it would not prevent her office from getting a conviction in court.

Harris said an arraignment could be scheduled for as early as this morning.

Authorities said Bobby Brown has been violent before on public transit.

On Dec. 14, 2004, he was accused of punching a woman for no reason as she waited for train doors to open at the MacArthur BART Station in Oakland, BART spokesman Linton Johnson said. Bobby Brown was arrested on suspicion of misdemeanor battery, and although no charges were filed, he was sent back to state prison on a parole violation.

Bobby Brown had also been cited twice in 2003 for BART fare evasion.

The most serious crime on his record dates to July 13, 1999, when police said he shot at a Noe Valley man who confronted him for knocking on a woman's window at 11 p.m.

The man told him to leave but Bobby Brown fired at the man and fled, officials said. Bobby Brown was arrested on attempted murder charges and pleaded guilty to charges of assault with a deadly weapon.

He was given a three-year suspended prison sentence but was later sent to prison for violating his parole.

He has told authorities in San Mateo that he lived at an O'Farrell Street SRO hotel, but a clerk there said this week he had not been staying there for several months.

Bobby Brown's father, Bobby L. Brown Sr. of Richmond, declined to comment late Wednesday.