Possible Clues:

• Red warning device that might have a 'pull down' handle
• Shoot gangster? Weapon that might be raised with smoke
• Danger signal -- Capone has gun around!
• Warning apparatus
• Warning of a possible serious danger
• Warning device
• Genuine article installed by company that signals danger
• Siren, perhaps, with weapon, seen around US city
• It signals danger with shooter crossing a line
• Evacuation notice?