Plot hole: Detective Mason Storm has been in a coma for a number of years, so how is it that on the day he awakens from the coma, he not only has the strength to move his bed down corridors, but also knows the layout of the hospital?
Continuity mistake: When Segal and LeBrock are being chased across the field, and they drive the jeep through a gazebo, Segal is driving. However for a split second as the jeep passes through the gazebo Segal is in the driver seat of a right side steered jeep. The license plate also switches sides but reads correctly (left-to-right) indicating that the shot is not mirrored.
Visible crew/equipment: When Becker is shot while eating a sandwich and watching TV, the leads to his gunshot squib can be seen coming out of the bottom of his trouser leg as he reels back from the impact of the blast.
Deliberate mistake: When Steven Seagal and Kelly LeBrock are in the jeep, being chased through some fields by the cops, some of the shots of the jeep are flipped. Note the bullet holes on the windshield switch sides, as does the driver/steering wheel, the windshield wipers and the front license plate. As an aside, also note the numbers/letters on the license plate that have been altered via CG in the flipped shots.
Continuity mistake: The hit man stands in front of a bank of elevators in the hospital. He turns to run to the other bank and a hand reaches across to shut the elevator door as he approaches.
Continuity mistake: In the train station scene, when O'Malley is shot, watch the front of his shirt as he hides behind the cab so he can start shooting the bad guys. He was running away from them when he gets hit once in the back. Then, as he turns around to fire back behind the car, there are two bullet holes in his shirt with blood dripping down like he had been hit. But he was only shot once in the back.
Continuity mistake: Steven Seagal is wearing a suit and vest in the beginning of the film when he is all shot up. He is then wearing the same suit and vest later in the film when he recovers.
Continuity mistake: When Seagal and LeBrock first jump into the jeep to escape the bad guys at the house, the roof of the jeep gets shot up by a gunman above them. Seconds later, when they crash through the fence, the roof of the jeep is intact.
Visible crew/equipment: In the shoot out scene at the train station between Captain O'Malley and the bad guys, through O'Malley's shirt you can see the patch strip they use to make the fake bullet holes when he gets shot. You see it well because he gets shot in slow motion.
Continuity mistake: When two members of the hit squad start firing at Sonny at Mason's home, you can see Mason, who was shot only a few moments earlier, pulling up a blanket on the bed.
Continuity mistake: During the fight in the billiard room, Storm kills Jack Axel by stabbing him with a pool cue and Axel falls to the floor and dies with the cue still stuck in him. When Hulland enters the room shortly after, we see Axel still laying dead on the floor, but the pool cue is gone.
Continuity mistake: When Storm grabs the white van from the Chinese driver to go to the Senator house, the next two shots, the driver disappears.
Other mistake: Even though Mason Storm is avenging his family's slaying by corrupt cops and a politician, he has committed several crimes while doing so - he snaps the neck of a person when he has them incapacitated after a fight, then he commits 2 car jackings, then he holds someone at gunpoint, innocent or not he would have been arrested along with the conspirators for the murder and carjacking.
Revealing mistake: In the shoot out scene at the house when Seagal and Kelly Lebrock duck for cover in the living room you can see Seagal's stunt double as they hit the floor.
Answer: He survived the first attempt of his family's murder. There's no telling what he saw or heard. As for the masks, the bad guys were taking no chances, security cameras, cell phones and the unexpected eyewitness.