Luigi Mangione Smashes Open Beer With Head & Chugs It, Video Shows

Luigi Mangione, the suspected killer in the Brian Thompson murder case, was unafraid to let loose and have a good time during his college years ... going wild in a video from his time at the University of Pennsylvania.

In the video obtained by TMZ ... Luigi is seen repeatedly smashing a beer on his forehead before chugging down the alcoholic beverage. Several partygoers hype up Luigi during the party trick ... as he's filmed gulping down the beer.

A source tells TMZ ... the wild scene took place at a massive St. Patrick's Day party -- which explains the number of green shirts in the footage -- at the Ivy League school in 2019.

Per the source, this behavior wasn't unusual for Luigi, either ... with the insider describing LM as "the life of the party in college."

We're told Luigi often gave off total frat bro vibes .... but was still well-liked and popular -- which had to do with the fact that he was very kind, funny, naturally intelligent, and creative.

The source says Luigi -- who majored in computer engineering -- was a tech-oriented guy, who had a work-hard, play-hard mentality at school.

Luigi was in no way a loner, according to the source ... noting LM was not the typical person you'd expect to be a suspect in a violent shooting.

Like others who knew Luigi, the source tells TMZ that LM's arrest was "shocking and unexpected."

Luigi is currently facing second-degree murder and gun charges in connection with last week's fatal shooting of the UnitedHealthcare CEO in New York City. His lawyer previously stated Luigi plans to plead not guilty to the charges, as he fights extradition to New York after his Monday arrest in Altoona, PA.