The unidentified man who was killed and his wife were shopping at a Walgreens in Arlington, west of Dallas, when they witnessed a female employee who had been shot in the leg near the store entrance, an Arlington police spokesman told reporters at the scene.
The man went to his vehicle, retrieved his weapon and confronted the man who had shot the woman, Lieutenant Christopher Cook said.
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Gun owner trying to break up fight fatally shot in Texas parking lot
A weapons factory manager, left, explains mechanic details of a machine gun for visitors at a police equipment exhibition in Beijing Thursday, May 24, 2012. (AP Photo/Alexander F. Yuan)
A Stockholm-based think tank said in a report on Monday that China has surpassed Germany to become the world's third largest arms exporter. Exports of major arms from the world's second largest economy grew 143 percent over the years 2010 to 2014, compared to the previous five-year period, when China had ranked ninth globally. The report is from the Stockholm International Peace Research Institute.
A machine gun stands mounted on top of a China North Industries Group Corp. (Norinco) VT4 battle tank during the China International Aviation & Aerospace Exhibition in Zhuhai, Guangdong province, China, on Wednesday, Nov. 12, 2014. The air show takes place from Nov. 11-16. Photographer: Brent Lewin/Bloomberg via Getty Images
The Chinese people have just entered the fourth year of their war against Japan and they are making super-human efforts to strengthen their air-force, to produce their own armaments, and to train their officers in the methods of modern war. A machine gun factory in Western China are turning out ten to fifteen thousand a month, July 11, 1940. (AP Photo)
Tim Nordstrom torques a barrel extension on the barrel of a MA-15 rifle at MMC Armory, a division of Mennie Machine Co., in Mark, Illinois, U.S., on Wednesday, June 26, 2013. The Institute for Supply Management is scheduled to release monthly manufacturing data on July 1. Photographer: Daniel Acker/Bloomberg via Getty Images
Inspection tools sit on a workbench near a row of MA-15 gun barrel's at MMC Armory, a division of Mennie Machine Co., in Mark, Illinois, U.S., on Wednesday, June 26, 2013. The Institute for Supply Management is scheduled to release monthly manufacturing data on July 1. Photographer: Daniel Acker/Bloomberg via Getty Images
Nicole Doran, right, and Samantha Lenhart assemble bolt sub assemblies for MA-15 rifles at MMC Armory, a division of Mennie Machine Co., in Mark, Illinois, U.S., on Wednesday, June 26, 2013. The Institute for Supply Management is scheduled to release monthly manufacturing data on July 1. Photographer: Daniel Acker/Bloomberg via Getty Images
RANCHO CUCAMONGA, CA - JULY 15: Tractors work in unison to scoop up 12,153 illegal guns and other weapons confiscated from criminals to melt them down and convert them into steel rebar at the Tamco Steel mill on July 15, 2008 in Rancho Cucamonga, California. The reinforced steel bars made from the recycled guns and weapons during the 15th annual Project Isaiah, supervised by the Los Angeles County Sheriffs Department, will be used in freeway and highway construction projects. California law demands that confiscated weapons be destroyed. (Photo by David McNew/Getty Images)
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"The suspect was trying to leave in the car. That's when the good Samaritan pointed his firearm, trying to get the car to stop," Cook said.
The suspect exited his vehicle, shot the man in the head and fled the scene, he said.
The suspect, thought to be the husband or the boyfriend of the woman who was shot, eventually surrendered to authorities in another county. The woman was taken to a local hospital with non-life threatening injuries.