The email came from info@splunkcareers.us. The first thing to do when receiving such an email is search for the company home page (in this case: splunk.com). If the second and top level domains don't match, you have a scammer. Companies never use addresses outside of their domain.
They asked the person to buy things and then send them somewhere via UPS. This is THE hallmark of a scam.
Next is the linking of a "company" account to your personal card. This NEVER happens.
Finally, asking you to buy things on your personal card and expense them is almost never done before you've actually started work (I say "almost" because some very small 1-2 person startups who don't know any better might do this even though they shouldn't).