Idaho State police are still trying to determine what led Matthew James Stapleton to lose control of a 1986 Toyota 4-Runner Tuesday afternoon at the Ten Mile Road overpass before a crash that killed him and his 83-year-old mother.

Ada County Coroner’s officials identified the 49-year-old Stapleton as the driver of the 4-Runner.

Betty Jean Stapleton was pronounced dead at the scene of the crash, which happened around 12:15 p.m. Tuesday. Paramedics took Matthew Stapleton to Saint Alphonsus Regional Medical Center, where he was pronounced dead shortly after 4 p.m.

The cause of death for both Stapletons, who lived in Nampa, is listed as blunt force trauma and the manner of death is listed as accidental on coroner’s reports.

Idaho State police say Matthew Stapleton was driving the 4-Runner on eastbound Interstate 84 when he drove on to the Ten Mile Road off ramp, failed to stop at the intersection at Ten Mile, crossed all lanes, then kept going. ISP officials say the 4-Runner went over the on-ramp embankment, causing the SUV to roll over and eventually coming to a rest on its top.

Both Stapletons were wearing seat belts, police said.