An 18-year-old Maple Grove man was arrested Tuesday after he allegedly pushed an 8-year-old boy off a waterslide in Apple Valley, causing him to fall 31 feet to the ground, police said.

The man is expected to face criminal assault charges, officials said. The Star Tribune generally does not name suspects before they are charged.

The man and the boy, whose name was not released, were waiting in line to ride down a waterslide at the Apple Valley Aquatic Center on Tuesday afternoon. They did not know each other and had not talked while in line, according to police and witnesses.

Once they reached the top of the slide platform, the man picked up the boy and pushed him over the railing, according to police. The boy fell 31 feet to the ground.

The boy was conscious and breathing when police arrived around 1:35 p.m. He was taken to a hospital, where he is in stable condition, according to police.

“He’s had a number of broken bones and will have to go through a number of surgeries,” Apple Valley Police Capt. Nick Francis said.

Police believe the man may be developmentally delayed, Francis said.

“When we spoke with him, he was able to tell us that he knew what he did, he knew what he did was wrong, he knew what he did was going to hurt someone,” he said.

Thousands of visitors use the Aquatic Center each season, which runs from June through August. “It’s been open for 20 years, and this is the first incident where anything close to this has happened,” Francis said.

The Aquatic Center was closed for the rest of the day Tuesday.