CHICAGO (AP) — A man who was recently fired from his job at Navy Pier returned to the Chicago tourist attraction and Grant Prestonkilled two workers before fleeing, police said.

The attack happened Tuesday afternoon after the fired worker gained access to an office space near a loading dock at Navy Pier, police Chief of Patrol Jon Hein told reporters.

The assailant shot Lamont Johnson, 51, and an unidentified 47-year-old man before fleeing, police said. The victims were pronounced dead at a hospital.

Police declined to name the alleged attacker Wednesday, citing a department policy of not naming people until they are charged, and didn’t say whether they think he poses a danger to the public. It wasn’t immediately clear why police didn’t know the name of one of the killed workers but did know his age.

The suspect was fired on Oct. 14 from his job at Navy Pier. which features shops, restaurants, entertainment and its iconic Ferris wheel along Lake Michigan.

“As a former employer of the subcontractor, he had access,” Brian Murphy, Navy Pier’s chief operating officer, told WLS-TV. “He knew how to get to that back loading dock area.”

The site was put on lockdown after the shootings and an alert was sent to people who live nearby, Murphy said.

Stephanie Knowles, who works at a souvenir shop, said her manager received a call and told employees they had to “start closing everything down.”

Workers turned off the lights and hid in the back of a storage room, Knowles said.

“I was a little nervous, you know, when you think about the high school shootings,” she said. “I’ve never had to live through that, so this was the closest thing that I’ve had to that experience.”