This particular replicator was a Tau'ri-built Replicator, one of two models created by Dr. Richard Poole as part of Project Archetype. It was designated as a Replicator, despite the fact that self-replication wasn't one of its functions. Dr. Poole created the Replicator in a way that it was immune to the effects of current Anti-Replicator gun technology. It was however susceptible to standard Earth-made projectile weapons, as it has a limited capacity to self repair. The Replicator wasn't functioned to integrate to society and when it escaped the lab it hid in isolated areas.
Lt. Colonel John Sheppard and Ronon Dex joined Ava Dixon (who was later revealed to be a Replicator) to capture Poole's replicator after it escaped the Stanton Research facility and killed two guards before it killed again. Eventually they tracked the Replicator's location and managed to have beamed it to low-Earth orbit, and was disintegrated on re-entry. (SGA: "Outcast")