As video journalist Carrie Antlfinger awaited a news conference outside a Chicago hospital where a gunman had killed three people a day earlier, a deliveryman waiting for the emergency room to reopen showed her a photo he had taken.

The cellphone photo captured a pivotal moment in the story – the shooter standing next to his first victim, his former fiancee, whom he had shot in front of the hospital.

Antlfinger, who had been dispatched from Milwaukee to cover the breaking story, immediately recognized the value of the image and the man’s firsthand account. While the deliveryman was at first reluctant, Antlfinger was able to persuade him not only to provide the AP with the photo but to go on camera for an interview describing what he saw: the gunman standing over the body with a handgun in his hand, police pulling up to the scene and the gunman shooting at police.

The video received strong online play and use by customers, including by USA Today and Yahoo News. The photo was downloaded more than 350 times by customers. And Antlfinger’s material proved central to the AP’s second-day coverage of the story, with the exclusive photo leading the story, which included an embedded version of the video.

Antlfinger’s scoop was part of an aggressive cross-format effort by AP staff to cover all aspects of the story from day one.

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Chicago Police officers respond outside Mercy Hospital on the city's South Side where four people were shot and killed, Nov. 19, 2018. Emergency room Dr. Tamara O'Neal was killed in the hospital parking lot by her ex-fiance, Juan Lopez, who killed himself after also taking the lives of a police officer and a pharmacy resident.

AP Photo/Amanda Seitz

Amanda Seitz, the AP’s Fact Check reporter based in Chicago, was dispatched after the initial reports of the shooting, following police cars to the hospital, where she gathered color and quotes in addition to using her iPhone to shoot the AP’s first photos and video. Michael Tarm joined Seitz at the scene, while colleague Don Babwin worked police sources. And soon after the news broke, Chicago-based video producer Bob Eller persuaded television station WLS to share its material, allowing the AP to offer customers strong video coverage from the start.

For recognizing a critical way to advance the AP’s reporting and then negotiating exclusive access to the photo and interview, Antlfinger wins this week’s Best of the States.