After a well planned ambush on an armored truck carrying arms, a cop must find the people behind it before the weapons hit the streets.

Agreed with the above - this reads like a standard police procedural episode. Ultimately, it's about a guy doing his job but what you need is for it to be about a motivated guy doing something out of the ordinary. Could his brother or sister be involved in a gang and he knows that the weapons were taken by a rival gang?

While the premise is good, I think you may need that one extra element to hook the idea with the reader
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"When MS-13 steals a huge arms shipment, a mercurial police translator is teamed with a hard-nosed?detective to find the shipment before the guns hit the streets."

This is a good solid base for a story. But why this crime and this cop. In Heat Robert De Niro breaks his own rule and forms a connection to someone.

It's a cop story that is really about two men that are having relationships issues because of their involvement in crime.