3 missing US soldiers found dead in Lithuania, search continues for 4th soldier

[LPBBEAR]

9. Why assume accident?

An accident would put the bodies in the vehicle, not elsewhere. Cause of death may be released but if the cause was execution gunshots we may not hear about it for security reasons.
My guess at a possible scenarios.

Out on patrol
Stumbled into a Russian/Belarus infiltration unit
US Soldiers Captured and executed
Vehicle dumped in swamp to slow down discovery
4th soldier possibly held for interrogation

or

Out on patrol
4th soldier goes off the deep end
murders his fellow soldiers
Vehicle dumped in swamp to slow down discovery
4th soldier on the run.

Can't think of a logical explanation for the bodies not being with the vehicle that conforms to "accident".