Mark Salling's Final Days: 'Glee' Alum 'Isolated Himself' Amid Child Porn Case, Source Says

In the days before he died of apparent suicide at 35, Mark Salling led a secluded life.

“He was close with his family, but as far as friends go — he maybe had those acquaintances he communicated with every once in a while, but he pretty much isolated himself,” a source tells PEOPLE of Salling, who was best known for playing Noah “Puck” Puckerman from 2009-15 on Glee.

“He didn’t really have a relationship with too many people,” the source adds.

Salling’s death comes just a month before he was to be sentenced to prison for possession of child pornography. He was arrested in Dec. 2015 after LAPD’s Internet Crimes Against Children unit obtained a search warrant for his home in Sunland, California. Federal investigators say they found more than 25,000 images and 600 videos depicting child pornography on computers and thumb drives that belonged to Salling. The content depicted children as young as 3 years old being abused, according to court documents.

He pleaded guilty to possession of child pornography involving a prepubescent minor in October. After striking a plea deal in December, he was due to be sentenced in March and expected to serve four to seven years in prison. According to documents obtained by PEOPLE, Salling had to register as a sex offender and enter a treatment program; have no verbal or electronic contact with anyone under the age of 18; stay 100 feet away from schools, parks, public swimming pools, youth centers, playgrounds and arcades; and pay $50,000 in restitution to each victim.

“The Mark I knew was charismatic, he was funny, he was musically talented — he was a really cool person,” says the source, who adds that the actor was “never really into drugs.”

“This other dark side of him was completely shocking to everyone close to him,” says the source. “Close people who didn’t talk to him are still sad about it. They loved him because of the person he was before all of this happened. There’s a level of sadness with everyone, but the sadness is from afar.”

A second source close to Salling tells PEOPLE that she hadn’t spoken to the actor in while, and that he restricted contact to his parents and a roommate after his arrest in connection possession of child pornography.

“His career was off the boil, though; he was kind of the quarterback that peaked in high school, still dining out on Glee,” the second source says. “Eventually, though, he started to focus on his music, which seemed like a good thing. That’s where he should have been focused to start with. But then the child porn thing came out, and people were so shocked. … It quickly started to become clear it was real, and then the few people still around him iced him out.”

But in his heydey, Salling was a popular fixture in the club scene, this source says.

“Mark was fun, he had the charisma — sure, some was because he was on a show, but he also had that X factor you know?” the second source says. “He always had girls around him.”

Salling’s attorney Michael Proctor confirmed the news of the troubled actor’s passing in a statement to PEOPLE on Tuesday.

“I can confirm that Mark Salling passed away early this morning,” said Proctor. “Mark was a gentle and loving person, a person of great creativity, who was doing his best to atone for some serious mistakes and errors of judgment. He is survived by his mother and father, and his brother. The Salling family appreciates the support they have been receiving and asks for their privacy to be respected.”If you or someone you know is considering suicide, please contact the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).