A member of environmental group is killed while trying to get info on a company's acts of pollution. Later members of the company are being killed by bombs. The ATF investigates and the leader of the group is brought in. While he is not the one who is doing it, he is keeping something from them, so they keep him under surveillance.
Greenmail
When 3 environmentalists break into a chemical plant, they're discovered and one's shot by a guard. The guard et al are targeted with bombs. A DC agent joins the investigation.