get as passive auxiliary: He got caught.

Get + past participle can be used to make passive structures in the same way as be + past participle. This structure is mostly used in an informal style. It is often used to talk about events that happen by accident, unexpectedly, or outside one’s control, and that have good or bad consequences.

• I get paid on Fridays.
• She’s always getting invited to parties.
• My watch got broken while I was playing with the children.
• He got caught by the police speeding through the town centre.

The passive with be is preferred for longer, more deliberate, planned actions.

• The Emperor Charlemagne was crowned in the year 800. (It would be strange to say Charlemagne got crowned …)
• The new school will be opened by the Prime Minister on May 25th.
• Our house was built in 1827.