The Horizon Air worker who stole an airplane from Seattle’s airport and took it for a joy ride crashed intentionally to commit suicide, the FBI said in a report that concluded he had no apparent ties to terrorism.

Ground service agent Richard Russell, 28, acted alone and no charges are planned in the August incident, the agency said in a statement released Friday. Investigators found no explanation for why Russell, who wasn’t a licensed pilot, wanted to steal the empty plane and kill himself.

“Interviews with work colleagues, friends, and family—and review of text messages exchanged with Russell during the incident—did not identify any information that would suggest the theft of the aircraft was related to wider criminal activity or terrorist ideology,” the FBI said. “Although investigators received information regarding Russell’s background, possible stressors, and personal life, no element provided a clear motivation for Russell’s actions.”

Similarly, an investigation by the Transportation Safety Administration uncovered no violations of safety regulations by Horizon or Seattle-Tacoma International Airport, the agency said in a statement also released Friday. Horizon is owned by Alaska Air Group Inc.

The TSA found the airline and airport “to be in compliance with all security requirements,” it said.

The aviation security agency said it’s looking at ways to “strengthen security in all aspects of the airport environment.”

“This incident was a very difficult moment for us and many others,” Horizon Air president and CEO Gary Beck said in a statement. “We remain grateful to everyone who offered support to our employees, the family of the deceased employee, and the communities that were impacted.”

The U.S. National Transportation Safety Board analyzed data from the flight and reviewed a cockpit recording from the plane’s two crash-proof black boxes, the FBI said.

Russell spoke extensively on the radio with with air traffic controllers after taking off without permission. He was “just a broken guy,” he said at one point, as a controller tried to convince him to try landing the plane. “I got a lot of people that care about me and it’s gonna disappoint them to hear that I did this.”

Piloting Skills

The Port of Seattle, which operates the airport, is also performing a review of the incident in conjunction with TSA and an industry working group to determine if additional actions are needed. It is examining new technology, security measures and “employees’ well being and health,” it said in a statement.

The plane, a Bombardier Inc. Q400 turboprop, was slipping partially sideways during its final dive, the FBI said, an indication that Russell lacked sophisticated piloting skills.

Nevertheless, “the airplane appears to have remained in control, and the final descent to the ground appears to have been intentional,” the FBI said. “If the pilot had wanted to avoid impact with the ground, he had time and energy to pull the column back, raise the nose and initiate a climb.”

Russell had legitimate credentials as a Horizon employee to gain access to the plane, according to TSA and the FBI. As part of his regular duties, he was familiar with how to switch on a small turbine engine aboard the plane that’s used to provide electrical power and to start the main engines. He also knew how to maneuver the plane on the ground, according to the FBI.

Instructional Videos

While there was no evidence Russell had received formal flight training, he’d searched the internet for flight instruction videos, the FBI said.

Russell arrived for work on Aug. 10 at 2:36 p.m. He entered the plane at 7:19 p.m. and began starting the engines within minutes. He briefly left the plane and used a tow vehicle to turn the plane’s nose toward the taxiways leading to the runways. At 7:32 p.m., the plane began moving, the FBI said.

The plane flew for 1 hour and 13 minutes before crashing on thinly-populated Ketron Island in Puget Sound, about 25 miles (40 kilometers) from the airport.