Four people have been shot dead on an early morning commuter train near Chicago.
Police said they were seated apart in two carriages and appeared to have been attacked while asleep in their seats as the train was moving.
Officers were called to Monday’s incident just before 5.30am and pronounced three of the victims dead at Forest Park station.
A fourth person died later in hospital.
The suspect escaped but was later arrested with a gun on another train, said Forest Park Police.
They said the attack appeared to be an isolated incident with no further threat to the community.
Information on the victims’ identities is yet to be released.
Forest Park is a suburb about 10 miles west of downtown Chicago and has a population of about 14,000.
Be the first to get Breaking News
Install the Sky News app for free
“It’s a horrible tragedy that four people are dead on Labor Day weekend,” said local mayor Rory Hoskins.
“Our police department and our fire department respond to this location probably more than any other location in our jurisdiction.”
Keep up with all the latest news from the UK and around the world by following Sky News
Read more from Sky News:
Motorcade carrying Tim Walz involved in crash
Elle Macpherson reveals she’s had breast cancer
A regular traveller on the route, Sean McNulty, said criminal activity is not unusual on trains in that area.
“You just kind of get used to it,” he told the Chicago Tribune. “I keep my eyes open because I want to know what’s going on around me at all times.”
The Chicago Transit Authority called the killings a “heinous and egregious act of violence”.
