Your first error was allowing the other agent in before you exited. Now you are stuck; do you put the key back in the lockbox and hope they access the key to lock the home, or do you put the key in their hands and hope they are who they say they are and still lock the property securely when leaving?

I would respectfully ask them to step out and allow me to complete my showing, secure the property and return the key to the LB.

I would ask them for their business card. If an electronic lock box I would ask them to run their card through it . I always lock the door when showing so this does not happen. And call the L.A.

I lock the door behind me.  If I happen to appear at the home at the same time as another agent ... and I access the key first, they are asked to wait until we are finished ... and then they access the key via the lockbox.  If conditions don't permit them waiting (rain, cold, too hot) then I let them in with us. If they do not leave before I do ... they need to access the key ... via the lockbox ... holding them accountable for being in the property. 

I wouldn't have allowed the agent in before I place the key back in the Lock box

Michael J. Perry I would ask them ask them to open the LB so they are recorded as showing the property. Jeff Dowler has a good answer about locking the door while showing.

Return key to lockbox.

Call the listing agent and tell them you are leaving and Blank agent entered with their clients before you could lock up.  This puts them on notice that Blank agent won't show up on the lock box entrance record.

 Put the key back in the Supra box, close it.   Then hand it to that Agent and ask them to re-open it with their code.

It has never happened, but if an Agent refused, or rushed in and out without resetting the Lockbox, I would take a picture of them and/or their car, then telephone the Listing Agent.

I put the key back in the lockbox so that there is a history or my entry and exit and history of the next agent's entry and exit. 

Follow all instructions explicitly. If they say to lock up when you leave, then do so and explain to anyone there what and why you are doing

Wouldn't happen . . .   I lock the door after I enter.  I don't need any unexpected visitors; friend or foe!

I would lock up and let them open with their key!

This must be an extension of Verns question on double booking.

It would be wise to kick them out until they have signed in under their agents code.

Ditto Kenneth J. Jones No way I want to be responsible if next agent does not lock door, etc.  Erie does not use electronic LB 

I would mention that we were just leaving, and to just give us a few minutes.  Then I would finish our Home Tour, lock the door and return the key to the lockbox.  They need to be registered on the lock box, and this way you know you locked the door and did not let anyone in who may or may not belong there Michael J. Perry.  Just saying they will leave a business card would not impress me, because I wouldn't even know if they were a realtor! 

Lock, check doors are locked and no one is inside.

Return the key to the electronic lockbox and let the next agent open it for the needed registration.

Jeff Dowler nailed this one!

We don't have electronic LBs here yet so no isse with that. I would check with the agent and make sure he/she knows how to lock up. I'd also text the listing agent mentioning we finished touring the house and so-and-so is now touring it.

Michael J. Perry - if I know the agent, I hand over the keys. If not, put the key in box and expect that agent to open the LB.

Say hello - ask the agent to open the lockbox with their keycard

If I know the agent I will hand over the keys, but If ido not, I lock them in the box.  If it is electronic, I lock them so the listing agent has a record.

Put the key it the lockbox, lock it and have the new arrival open it up before you leave.

In my market we will know the other agent showing the property. I don't have a problem with going out the door, and letting the other agent do their thing. I realize in larger markets this could be a concern. 

I ask the agent to log into the lockbox and get the key so their visist will be registered. I don't want them left in the house on my log in.

If it is supra, I'll put the keys back, so that agent uses his key to open and leave his/her info. If it is a combo lockbox and the agent told me the right combo, I would just pass the key. 

Put the key back in the lockbox and tell them it is all yours. Then shut the locked door. Actually I have the key in my pocket and lock the door after we walk in.

if the agent is already in the home, I'd place a phone call to the listing agent and let the agent know the agent entered without going through the LB... I'd get a card from the agent, too....

I make them use the lockbox to record them being there.  I usually lock the door when I can too.

Get their card or ask them how they plan on getting registered in the LB?

I've had this and when I let the agent stay, he left the deck door wide open. Luckily, I went back to check and took care of it. After that incident, I ask the agents to wait and then open the door with their key pads to allow the LB to register who was there last. 

At the least have the other agent unlock the lock box with their own ID if an electronic lock box so the listing agent will have a record of the showing.  For manual lockboxes at the least have the agent tell you the code so you know they have access.

Close the door and tell the agent I am going to put the key back in the lockbox so the listing agent will have a record of the showing.