A US passenger opens plane's exit door! What happens next?

Weird incidents related to flights are happening quite frequently these days. And the latest incident is related to a man in the United States, who allegedly opened an emergency exit door aboard a plane, which caused its emergency slide to be activated moments before it was set to take off. If reports are to go by, the said man has been arrested after the incident.

Reportedly, the incident took place at the Los Angeles International Airport. Revealing more about the incident, the Los Angeles Airport Police stated that the passenger apparently rushed to the front of the plane, while it was pushing away from the gate, and asked the flight attendant, "What do I do now?"
Although the flight attendant kept asking the man to sit down, he ran to the plane's emergency exit doors, turned the latch, opened the door, and slid down the deployed emergency slide.

What next? Well, this incident forced the plane to stop, whereas the man who opened the emergency exit jumped onto the back of a baggage cart, where luggage workers helped him get down, after which the airport police got there.
The airline, in a statement, said that the flight returned to the gate due to an unruly passenger, who was initially detained by Delta staff ahead of being arrested by local law enforcement.

The Los Angeles Airport Police further added that the FBI has been notified about the event. Reports have it that the Airport Police responded and detained the passenger for further investigation.
Following the incident, the unruly passenger was taken to a local hospital for mental evaluation, while the other passengers were escorted off and moved to another plane. Due to this incident, the flight was delayed by 3 hours!