Scar is possibly the only person in Amestris to be able to kill so many State Alchemists in such a short period of time.
He was first shown as a mysterious, powerful serial killer in Central after Edward Elric had his mishap with Shou Tucker, an Alchemist that was extremely bent on human and Chimaera fusion. The man was insane, and turned his daughter into a chimaera fused with his dog.
Scar laid his justice on the man quickly after the govt. police had left the main estate for a short period of time.
It was raining in Central at the time, and two guards were standing at the door with weapons, guarding the insane man's home.
"I need to go in." Scar had said, walking up the stairway and almost into the house, when a military guard stopped him.
"Sir, we're sorry, but the estate is off limits until the main police get back onto the premises...so scram." the young man with a shotgun said. Scar put his hand to the mans forehead and instantly blew him to pieces, and, before his partner could react, killed him too.
As he walked into the room with the insane man sitting down, he thought about all he'd been through as an Ishbalan. The pain, the suffering, the attempted genocide of his race. For all these filthy State Alchemists had done they may as well have annihalated their race.
Forced to retreat at the sight of a non Ishbalan...to hide in the sewers like a filthy rat...he hated it. And so that was why Ishbala had chosen him to lay out her divine justice on the State Alchemists. How long he had waited to stop the heathens that defied god and twisted everything they knew. And how efficiently he'd done it so far, too. With all of the power he had behind him it was no wonder they'd nicknamed him Scar in Central.
Scar...the X shape on his forehead made him infuriated to think of what he'd done to recieve the blow.
A few memories popped back into his head while saying these things and he was unable to hold in hsi emotions very well, so he just stopped for a few moments.
Speak no more, justice was to be fulfilled. He walked up to the man, obviously he had turned insane from all of the chaos and the loss of his child, but it was all his fault. Scar could feel no emotion in taking his life, he was one of the State Alchemists. The ones that sinfully created things and twisted them from God's true intentions. He was sickened by them as an Ishbalan.
"Nina...Nina...." was all Shou would say. When Scar walked in, he was surprised, and asked him how he got in, only to have Scar reply, telling him that the Judgement of God had found him.
He walked outside after killing him, and started smoking a cigarette and began to lean against the wall, when he heard a quiet voice. "Dad...dad..." it said. The poor beast, he thought. The young girl fused within her pet. Scar looked at her deformed body, and knew what it needed. Tears streaked down her face, and he ended her suffering, knowing she would not go to the same place as her father. Standing in the rain
Scar began walking away from the house that he'd just commited murder in, and started to head towards Central. There were supposed to be a bunch of State Alchemists and other military personnel there today. A perfect time for him to take Colonel Roy Mustang down for good. Roy had been a major thorn in his side for a while, and Scar figured today was going to be a good day for him. Roy had no power in the rain as far as his research had shown.
He began briskly walking again when he ran into a guard standing straight in front of Edward Elric , the youngest of the State Alchemists. Lucky for Scar, they didn't see him. well, the guard didn't but, Ed did, and so he commenced to kill the guard while chasing down Edward Elric, to destroy one more nuisance in the world. Edward Elric began running as fast as he could, scared out of his mind from the serial killer behind him.