The new cameras

After the theft, the base installed new cameras. They aren't switched on yet, but they're already getting a lot of praise. Some clues in this case come as riddles. If one stumps you, a hint will solve it. Four people and one grenade: one person per row, one per column. Whoever is left alone with it in the same room is the one you're looking for.

Suspects

• Abel, the new cameras technician: He installed thirty cameras. They still need electricity, which is another tender.
• Bertília, the soldier on sentry duty: She stands guard at the depot door. The door still has no lock, but it now has a camera.
• Constâncio, the public relations major: He gave a press conference on the new cameras. He showed photos of the cameras switched off.
• Delminda, the maintenance corporal: She'll switch the cameras on as soon as the cable arrives. The cable is coming from very far away.