Sunday evening was scheduled to be SpaceX's third attempt at its second launch of the year. However, a series of unexpected set backs, which began with a boat, ultimately led to an abort for the evening.
It was definitely a close call. The countdown clock actually reached T-00:00:00 and the rocket looked like it was about to lift off at 7:21 p.m. ET, when all of the sudden the computer in control of the rocket shut the engines down.
Here's what the abort at the very last second looked like — you can actually see the engines begin to fire:
Despite Sunday evening's scrub, SpaceX reported that its Falcon 9 rocket is still healthy.
Why the launch was aborted
The problem began around 6:45 p.m. ET when a boat strayed too close into the danger zone. The launch was temporarily held to give the boater time to vacate, and SpaceX was still expecting lift off, albeit a little later than scheduled.