Las Vegas police may have prevented a mass shooting during Tuesday’s Stanley Cup final by detaining 33-year-old Matthew DeSavio after he threatened to carry out a massacre online.

“I’m coming for you guys tonight and I hope you get every [expletive] police officer in Vegas Golden Knights there to defend you!” said one message, according to local station KLAS. “Hope Sin City is ready for the Mandalay Bay massacre part duex [sic].”

In October 2017, a shooter who was residing on the 32nd floor of the Mandalay Bay hotel in Las Vegas opened fire on the Route 91 Harvest music festival that was going on below, killing 61 people and injuring hundreds more. It continues to be the biggest mass shooting in American history.

Around noon on Tuesday, Las Vegas Metro police allegedly responded to a shop where DeSavio was allegedly making the threats and detained the suspect. According to reports, the suspect has a long history of harassing someone at that company.

Cops had also been contacted by someone concerned with postings DeSavio made to Facebook about “conducting a mass shooting at T-Mobile Arena” where the Vegas Golden Knights won their first NHL championship Tuesday night.

The suspect reportedly asked police if they’d seen his Facebook postings when he was taken into custody. One of those messages referred to the 2017 Las Vegas slaughter as “just a preview.”

Law law enforcement says that the suspect threatened to replicate the music festival slaughter on Facebook in October. DeSavio reportedly had a psychological evaluation mandated by a Nevada court in November, but the case against him was dropped because the state couldn’t deliver the service on time.

DeSavio is now accused of aggravated stalking and making a false threat relating to a terrorist act.