They can, but may they? And the answer is, yes with qualification.
The S.Ct. has held:
"The use of deadly force to prevent the escape of all felony suspects, whatever the circumstances, is constitutionally unreasonable. It is not better that all felony suspects die than that they escape. Where the suspect poses no immediate threat to the officer and no threat to others, the harm resulting from failing to apprehend him does not justify the use of deadly force to do so. It is no doubt unfortunate when a suspect who is in sight escapes, but the fact that the police arrive a little late or are a little slower afoot does not always justify killing the suspect. A police officer may not seize an unarmed, nondangerous suspect by shooting him dead." Tennessee v. Garner, 471 U.S. 1 (1985)
There is some latitude in the reading of the current facts. Did the officer believe the man was armed and presented an immediate threat to others? Was either belief reasonable given the circumstances?