It's OK to switch from past tense to "historical present" when you're describing quick action.

Tense depends on mood and audience. For short stories - try to use active present tense when possible - it's more "action" oriented and draws the audience into the story as an active participant as opposed to spectator.

For longer stories - you'll want to mix tenses to give the audience relief from "the action", build up the suspense - then action again.

Precisely as both @tommann and @tigertiger note.