Lord Revan wrote:we know for a fact that close range stun setting shot from a hand phaser can still kill the target, it was used to kill the assassins in TUC, so it's not at all impossible the much more powerful ship phasers could cause the same effect at even greater distance.
Better than "not impossible", it's been demonstrated, in Galaxy's Child - Picard tried to shoo off a space whale with a minimum-power phaser shot and ended up killing it.
Worf kept firing even after it broke off its own radiation field. He fired for too long. Plus it was giving birth
Worf was just upset that he wasn't allowed to fire photon torpedoes at it. And If he'd had his way, he would have shot the baby too, just in case. Then searched the entire sector for other space whales to hunt.
"I reject your reality and substitute my own!" - The official Troll motto, as stated by Adam Savage