It should be a criminal case, not a civil case

That is the reason cops ask you: do you want to be a witness. The police will do investigation and if they find violation of gun law or criminal law, it is the government who will sue this woman.

So you don't have to hire a lawyer or spend a penny. The government prosecutors do the work and pay the bill.

However, as a key witness, you have to spend a lot of time on this case.