This was either an accident, or the plane was the target, and the helicopter was the weapon.

We need to know who was on the plane. And hopefully it wasn't anybody about to testify in important matters, etc.

Plane was on predictable track, and assigned to a runway rarely used (per ABC news report tonight). Helicopter flew irregular path, then rose to meet altitude of plane AND changed direction to intercept in last few seconds of flight.

Maximum allowed height for the helicopter was 200 feet, which is where it was up until 37 seconds before impact. Surging from 200 feet to 350 just seconds before impact is a deliberate maneuver and takes considerable power to climb.