SACRAMENTO, Calif. -- A man took a coconut cream pie from a grocery bag, grabbed Sacramento Mayor Kevin Johnson from behind and smacked him in the face with it at a charity event, leading the former NBA star to start swinging and then tackle the man who was left battered and facing assault charges.

The pie wielder and local activist, Sean Thompson, 32, said Thursday that the mayor overreacted, sending him to the hospital for nine stitches before he went to jail. He said he was angry Johnson devoted so much political energy to an arena for the city's basketball team and not to other needs such as education and homelessness.

The mayor was greeting people eating at an outdoor charity dinner Wednesday night at Sacramento Charter High School when Thompson pulled Johnson back and shoved the pie in his face, said Johnson's chief of staff, Crystal Strait.

"There was no throwing of the pie," said Erika Bjork, who works for a professional soccer team in Sacramento and saw the encounter up close. "This was a direct assault. It just happened that he had a pie in his hand."

Bjork, whose boss is a major donor to Johnson, said the mayor looked shocked and swung at Thompson multiple times, but she didn't see him land any punches.

Thompson had red and blue bruises and a roughly 1-inch line of stitches under his left eye when he spoke to The Associated Press in jail.

"When I threw the pie at him, right at that moment, I shouted at him. I said, `You need to better represent me," Thompson said.

He said the mayor turned and hit him at least twice "and pretty hard." Thompson said he covered his face and started to move away but was quickly surrounded by people and kept taking hits. He couldn't tell who delivered the blows.

Thompson said he expected to be tackled by police but was caught off guard when the punches came from the mayor. He said he has no regrets but was surprised to be facing a felony, assaulting a public official.

He was held on $100,000 bail and was expected to be formally charged Friday.

Johnson's signature achievement in office was getting a $550 million arena built for the Sacramento Kings, which Thompson said took attention away from other issues.

Cres Vellucci, who organizes legal support for activists at the National Lawyers Guild in Sacramento, said people in the social justice community are concerned about Thompson's safety and Johnson's physical response.

Prosecutors will review the case, including the mayor's reaction, after receiving the police reports, likely on Friday, district attorney spokeswoman Shelly Orio said.

"Whether you're hit in the face with a pie or a fist, you've been assaulted and you're generally allowed to respond with similar force," said Rory Little, a former litigator and professor at University of California Hastings College of the Law.

Johnson's response "probably is not a disproportionate reaction, though it might not be the reaction we want our public officials to have," Little said.

Vellucci wrote in an email that he met Thompson five years ago and described him as a nonviolent person who participated in some of the first Black Lives Matter protests in Sacramento in 2014 and in Occupy Sacramento rallies before that.

Police and Johnson's chief of staff said Thompson was not previously known to the mayor and his staff. In an interview with local TV stations, Thompson said he's interacted with Johnson many times during city meetings for activists and that the mayor often appears disinterested and unengaged in community members' concerns.

Johnson is well-known for his efforts to revitalize Oak Park, a predominantly African-American neighborhood.

He's a graduate of the high school where the event was held Wednesday and brought it back from the brink of dissolution in the early 2000s by incorporating it in a system of charter schools he founded to help disadvantaged communities.

Johnson, who had a long career as an NBA All-Star with the Phoenix Suns and a brief stint with the Cleveland Cavaliers, has about two months left as mayor. He decided not to seek a third term.

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Associated Press writer Jonathan J. Cooper contributed to this report.

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This story has been corrected to show that the first name of Cres Vellucci was misspelled Chris and that Thompson had injuries around his left eye, not his right.