Pulsar, being a non trusting soul, would supply the "Alien with a weapon after checking to ensure that he was DEAD. Fire a couple of shots. and blast him to atoms after hiding anything found on him. when the "agents" arrive, say that the alien attacked him and he had no choice except to blast him.
Invite the feds to leave after they clean up the mess. and if there is any problems, oops.
Investigate the allegations and contact several contacts in the government that he has known for years and find out where the Prez is and ensure that he stays alive. As for the VP if it is shown that he is a Viper agent. he would find out that he suddenly weighed about 8 tons, right before he wound up weighing nothing and being thrown literally off the planet by the normal rotation of the world.
