PORTSMOUTH, N.H. – A Massachusetts man was being held after bolting from police, jumping a fence and sprinting across the runway at the Pease International Tradeport on Wednesday morning.

Jonathan Snow, 24, of Hamilton, Mass., drew the attention of police when he parked his car in an unusual way around 6 a.m., said Portsmouth Police Chief Brad Russ. When an officer asked him to move it, he bolted for the runway, where a plane bound for Bangor, Maine, was about to take off.

Russ said Snow also threw a backpack over the 8-foot chain-link fence to the runway. He would not say what it contained, but said “there were some materials in the knapsack that gave cause for concern.” He did not elaborate.

Police closed the Pan Am terminal and parking lot to isolate the man’s car, and at least one flight to Florida was grounded.

Russ said Snow was somewhat incoherent and may have a history of mental illness. He was not a scheduled passenger on any flight.

A Pan Am maintenance worker helped police capture him on the runway.