Jerry is in the Army and his best friend is killed in front of him by a roadside bomb. For several days afterward, Jerry's thinking becomes delusional and he holds a pose as if he were shooting his rifle. After about a week, he returns to normal. The most likely diagnosis is disorder.

The most likely diagnosis is brief psychotic disorder.

Explanation:

A traumatic event such as a tragic loss or a violent accident can trigger an state of alteration and disconnection from reality. Brief reactive psychosis is a rare psychological disorder in which periods of psychotic behavior occur suddenly and of short duration. These psychotic behaviors can range from hallucinations, delusions or confusion among others. Sometimes psychotic symptoms appear suddenly in response to a situation of great stress, although the symptoms can be very intense, recovery occurs within a few days, in other words, normally the symptoms of reactive psychosis resolve on their own in a period of no more than a month.