Bus driver shooting linked to sniper

Washington police have linked yesterday’s shooting of a bus driver to the sniper.

Microscopic clues on bullets and fragments have allowed US investigators to link shootings carried out by a deadly sniper terrorising the Washington area, but authorities are still trying to pinpoint the gun used.

Ballistics evidence in ten of the cases revealed that a .223 calibre bullet was fired from the same rifle, said Joseph Green, spokesman for the Treasury Department’s Bureau of Alcohol, Tobacco and Firearms. Bullets were too damaged to be helpful in two cases.

The sniper has now killed 10 people and critically wounded three others in Maryland, Virginia and Washington since Oct. 2.

In Tuesday’s attack, a bus driver was shot in the chest and killed in Aspen Hill, Maryland, 15 miles from Washington. A police task force was investigating as if the shooting was related to the serial sniper.

Narrowing down the exact make and model of the gun used is tricky. “Upwards of 100 different rifles” use that ammunition, said ATF spokesman Jim Crandall. All kinds of rifles use a .223 calibre bullet, including guns used in sporting activities, military weapons, such as the M-16 rifle, and some “assault type of weapons,” Crandall said.

Jim Kouri, vice president of the National Association of Chiefs of Police, said that the .223 calibre bullet tends to break up more than other bullets upon impact, a challenge for ballistics examiners. “It is very very difficult to make comparisons when you get a fractured or shattered round,” Kouri said.

Kouri also said that the .223 calibre bullet holds more gunpowder and travels three times faster than the popular .22 calibre used in many handguns and rifles.

“I don’t believe the sniper fires more than once,” Kouri said. “He doesn’t want any bullets out there in good condition.”

Every firearm has individual characteristics that are as unique to it as fingerprints are to human beings, ATF says.

However, an ATF database that helps firearm examiners match ballistics evidence contains only images of casings or bullets from crime scenes or from test firings of weapons used in crimes. It doesn’t include images of every gun sold in the United States, so a gun that hasn’t been used in a previous crime isn’t included in the computer database.

Firearms examiners analyse microscopic scratches and dents – on the bullets, their fragments or cartridge casings – to try to determine whether they were fired from the same weapon.

Grooves inside the barrel of a gun help a bullet travel with precision. When a bullet is fired, these grooves and other unique characteristics are imprinted on the bullet. When a bullet or bullet fragment is recovered from a crime, it is examined to see if a pattern of grooves and “lands” – the distance between the grooves -- can help determine the type of firearm that was used. Examiners also weigh the bullet or bullet fragments to try to identify the calibre and type of firearm.