As the story goes, one of the scientists there copped a warrant high grade enough for the Federal Marshals to come by and make an arrest. They were stopped at one of the gates into a more secure area, asked their business, and told that security would send out the person in question. The Marshals balked at this and demanded to be let in to make the arrest, lest the fugitive make good an escape somehow. After security asked for their requisite clearance, which the Marshals could not provide, it continued to escalate. Fingering their pistol butts, the Marshals insisted they were on lawful business and must be let in, while the guards with rifles replied that by all means the Marshals might make their entry but as armed intruders into a secure laboratory they would promptly get shot.

The pissing match took long enough that the fugitive was finally marched up to the gate and taken into custody before it could escalate further, at this point I believe the Marshals were on the phone with their higher ups trying to plead their case to be let in.