Reuben Foster, the 49ers’ inside linebacker, was arrested Sunday on charges of domestic violence, threats and possession of an assault weapon, police said.

This is Foster’s second arrest within a month. He was taken into custody on Jan. 12 in Tuscaloosa, Ala., for second-degree marijuana possession, meaning it’s for personal use, a Class A misdemeanor in the state.

A news release from the Los Gatos-Monte Sereno Police Department said Foster, 23, was arrested without incident in Los Gatos after police received a call around 9:15 a.m. about a disturbance. He was held on $75,000 bail, according to Santa Clara County Jail booking records. He was released at around 6:35 p.m., the Sacramento Bee reported.

The San Jose Mercury News reported that the accuser was a woman who was in a long-term relationship with Foster and that investigating officers found what looked like an assault rifle inside the home.

In 2017, he failed a drug test at the NFL combine for submitting a diluted urine sample. He was kicked out of the NFL combine in early March after an altercation with a hospital employee.

Foster, the NFL’s Defensive Rookie of the Month for November, ranked second on the team in tackles (72). The designation came after he missed five games because of a high ankle sprain and another because of back spasms.

General Manager John Lynch had previously said the 49ers were attracted to Foster for his enthusiasm and passion for the sport. The 49ers said they aided Foster with a strong support system that includes two former NFL linebackers on their coaching staff, Johnny Holland and DeMeco Ryans. Ryans, like Foster, also attended the University of Alabama.

At Alabama, Foster won the Butkus Award, which is given to the nation’s top linebacker, and was viewed as a top-10 pick in the NFL draft based on his talent. However, the 49ers traded up to select him No. 31 overall after he fell because of character and medical concerns. He underwent shoulder surgery to repair his rotator cuff after his final college season.

MMQB.com reported a team with a top-15 pick didn’t have Foster on its draft board because of his “immaturity” and “issues with life skills,” and that was before his failed drug test and altercation at the combine.

“I would anticipate people maybe questioning some of his character, but I would tell you his character’s what drew us to him,” Lynch said after the 49ers selected Foster in the first round on April 27. “When you start talking football with this young man, he lights up a room, and he’s a good kid. I believe in the kid, and I think it’s going to be — he’s going to be a great player for this organization for a long time.”

Foster is not the only athlete on the team to have faced domestic violence charges in the past year. In April, Santa Clara County prosecutors filed felony domestic violence charges against former 49ers cornerback Tramaine Brock. He was accused of trying to strangle his girlfriend multiple times, once when she was holding their 1-year-old child.

Brock was cut from the 49ers the day after he was arrested.

The charges against Brock were dropped nearly a month later due to insufficient evidence, according to prosecutors.

A week after Brock was released, Lynch was asked if he had a zero-tolerance policy with players when it came to domestic violence. He stressed the value of character and said each case would be viewed independently.

“As those situations arise and, hopefully, there won’t be a lot them, we’re going to treat each one of them as a unique and different situation,” said Lynch, speaking generally of off-the-field transgressions. “That’s what we did the other day. …

“I can also tell you that it wasn’t meant to send a message. I think you let those things happen organically, and we did what we felt was right in that situation. It was not easy and felt like it was something that we needed to do.”

Last month, after Foster’s arrest for marijuana possession, Lynch was optimistic about his future.

“He’s got to stay clean,” Lynch told NinersNation.com at the Senior Bowl. “We all know how special of a player he can be when he’s right. So he’s got to figure out how to stay healthy and stay out of trouble, but we believe he will do that.”

The team released a statement Sunday: “The San Francisco 49ers organization is aware of the report regarding Reuben Foster. We take matters of this nature seriously and are gathering all pertinent information.”

Under the NFL’s domestic violence policy, players are given a six-game suspension for a first incident and a lifetime ban for a second incident.

Sarah Ravani and Eric Branch are San Francisco Chronicle staff writers. Email: sravani@sfchronicle.com, ebranch@sfchronicle.com Twitter: @SarRavani, @eric_branch